This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. By the request of David Budil, we undertook the experimental study of a previously proposed design architecture for a novel peptide based nano-actuator. Budil's design is based on the [unreadable]-helical coiled coil portion of the yeast transcriptional activator GCN4, and it has been engineered to obtain an environmentally-responsive nano-actuator. The dimeric coiled-coil peptide consists of two identical ~4.5nm long and ~3 nm wide polypeptide chains. The actuation mechanism depends on the modification of electrostatic charges on histidine residues introduced at various points along the peptide, which is achieved by varying the pH of the solution, Previous molecular dynamic calculations have identified a set of peptide sequences that are expected to adopt the coiled-coil configuration and to exhibit reversible opening as a function of ambient pH. To test these predictions experimentally, the sequences were synthesized with rigid TOAC spin labels attached near the ends of the helices and the distribution of distances between the two labels determined by DEER spectroscopy as a function of sample conditions.